Although there is a generally held belief that limbic areas and limbic circuits of the brain are important in the production of emotion, the experimental evidence underlying this assumption is relatively sparse. Previous work in our laboratory has found that patients with injury to the left frontal cortex or left basal ganglia have a significantly higher frequency of depression than patients with other lesion locations. A recent study in which young adults were asked to recall a sad memory found that sad thoughts activated inferior frontal blood flow. Furthermore, frontal activation was bilateral in women but more left hemispheric in men. Other investigators have found that the cerebral hemispheres may be specialized for positive (left) or negative (right) emotion. This study proposes to use the lesion method to examine whether specific brain structures and hemispheres and perhaps gender play a role in the elicitation of emotion in the elderly. This will be done by examining normal elderly subjects and patients with unilateral brain lesions involving the head of caudate or the cerebellum to determine whether they experience subjective feelings of happiness, sadness, or fear following an emotion activation film. We will also determine whether the emotion is accompanied by physiological changes (i.e., changes in cerebral blood flow using (15-O) water and PET imaging), changes in frontal EEG asymmetries, changes in facial expression and changes in the autonomic nervous system. Preliminary studies in 8 normal elderly subjects revealed significant increases in blood flow following either happy or fearful films in the right amygdala. Left caudate, right and left amygdala, and thalamus increased with fear film. We have recently run two patients with stroke. One patient with a brainstem lesion showed the same direction of change and correlation between blood flow in the caudate and subjective rating of fear as normals while another patient with a left basal ganglia lesion showed decreased blood flow in structures that were consistently activated in normals and the brainstem lesion patient. This patient also reported attenuated positive emotion. These experiments will test the hypothesis that the intensity of emotions is mediate bilaterally but subjective experience of happiness requires intact left caudate (i.e., part of ventral lateral limbic structures), and sadness and fear require intact right caudate. Males will be more lateralized than and involve some different structures females. Blood flow changes in limbic but not other structures and frontal EEG asymmetries will be present when subjective emotion is experienced but will be absent when emotion is not experienced.